This invention relates to a valve. It is of particular applicability to a control valve that can be used as a settable coolant flow valve or as a dispense valve for beverages, e.g. to control flow of syrups and carbonated water to a dispenser. However, it will be appreciated that the invention is not limited to valves for such uses and they may equally find use, for example, in refrigeration units.
It is an object of the invention to provide a valve that is suitable for use as a control valve that can be maintained for a period of time in a partially open configuration or can be used in a situation where frequent opening and closing of the valve is required.
It is also an object of the invention to provide a valve which can be set with precision to any position in a desired range of partially open configurations between the fully closed and fully open positions and which can demonstrate a high degree of flow linearity between the fully closed and fully open positions.
Ingress of particles of dirt can cause problems in many valve systems. In addition to getting trapped between valve closure surfaces, where they can damage valve ports or seats, dirt particles can obstruct the cross-sectional area available for flow, and thereby alter predicted flow rates for a given valve opening. Thus it will be appreciated that this can be a particularly serious problem if a valve is particularly intended for use in a partially open, set configuration.
It is a further object, therefore, of the present invention, to provide an improved control valve in which the problems caused by dirt particles can be avoided or at least ameliorated.
Accordingly the invention provides a valve to control flow of a fluid, the valve comprising a housing containing a passageway between an inlet and an outlet of the valve, a closure member movable in the passageway from a first position in which the valve is fully closed to a second position in which the valve is fully open, the closure member engaging the wall of the passageway to seal the passageway, the wall of the passageway and/or the closure member defining a spiral groove which acts as a flow channel through which the fluid can flow on its passage from the inlet to the outlet when the valve is open, movement of the closure member from the first position towards the second position opening the flow channel through the spiral groove.
Thus flow through the valve can take place via the spiral groove when the closure member is moved from the first position to any partially open or to the fully open, i.e. second, position.
The groove may have a transverse cross-section that is constant or that increases in area in the upstream or downstream direction.
As the spiral groove may progressively increase in transverse cross-sectional area in the upstream or downstream direction, the valve can provide excellent linear flow and so that for a given pressure the flow rate may be more directly proportional to the valve closure member position than for conventional valves. This enables accurate flow modulation to be achieved, i.e. better control of the flow rate, over the entire operating range of the valve. Moreover, we have found that this construction of flow channel through the valve surprisingly results in reduced carbon dioxide breakout when carbonated water is passed through the valve.
However, a spiral groove of constant cross-section along its length also has useful application and can allow accurate positioning to provide precision from low flow through to high flow values through the valve.
The housing is preferably made of a substantially rigid material, e.g. metal, plastics material or ceramic material, and the closure member is also preferably substantially rigid and may be of the same material as the housing.
Suitably rigid plastics materials include, for example, acetals and acrylonitrile-butadiene-styrene (ABS) copolymers.
The spiral groove may be cut or molded into the material of the passageway wall or closure member by conventional means depending on the material used and it may, if desired, be defined partly in the passageway wall and partly in the closure member. It may, however, be preferred that the groove be defined in the passageway wall rather than on the closure member.
The closure member may carry one or more sealing rings to engage the wall of the passageway in the first position, i.e. the closure member may engage the wall of the passageway by means of the sealing ring(s) to close the outlet. Alternatively, sealing rings for this purpose may be located in the wall of the passageway. In an alternative embodiment, the closure member and passageway wall may be a precision fit in the first position to close the outlet without a seal.
As indicated above, the valves of the invention are particularly useful for incorporation into the dispense head of a beverage dispenser where they may be used to control the flow of fluids to be mixed at the dispense valve, e.g. syrup and carbonated water, or they may be incorporated into a coolant manifold for use in cooled beverage dispense systems. A typical manifold may contain a plurality of valves controlling outlets for the coolant, the valves being spaced along a common manifold. Each valve may comprise a housing containing a passageway from the common manifold to the valve outlet.
In a typical coolant manifold, the passageway of each control valve in the manifold will usually comprise at least a portion in the form of a right cylinder, and the closure member will be a corresponding cylinder of outside diameter slightly less than the internal diameter of the passageway, the closure member having an xe2x80x9cOxe2x80x9d-ring seal attached around its outer surface to seal against the passageway wall. In such an arrangement the spiral groove may extend for an axial length equivalent to almost the full length of the closure member although this is not essential and a shorter axial length may be found satisfactory for many circumstances.
The cross sectional shape of the spiral groove may be part-circular, part-rectangular or other shape but a preferred shape is of V-shape.
More than one spiral groove may be provided and the grooves may commence and/or end at different positions along the passageway whereby greater modulation variety and control may be achieved. Multiple grooves may also be of different cross-sectional area.
The pitch of the spiral groove or grooves, the number of turns comprising the spiral and the pitch relative to the cross-sectional area of the groove are all variables that can be used by the skilled man of the art to achieve his required flow through put and required modulation characteristics. For example, it will be appreciated that the longer the length of the spiral groove, the greater the pressure drop that will prevail as between the inlet and the outlet and the skilled man will take this into account in devising a suitable arrangement for his particular requirements.
The valve may conveniently be accurately set in any desired position from filly closed to fully open by means of, for example, a lever mechanism, a stepper motor, e.g. of the pulsed magnetically driven type, a proportional solenoid actuator, a diaphragm operated mechanism, or the like. When the valve is to be repeatedly open and closed a stepper motor or proportional solenoid actuator means may be preferred. Stepper motors, for example, can provide particularly accurate incremental increases or decreases in flow control.
Depending on the desired particular construction, the spiral groove or grooves in the passageway may increase in cross-sectional area in the upstream or downstream direction. In the latter case, the valves have the added advantage of having greater self-cleaning properties, i.e. larger particles can pass more readily through the valve in the open position without causing partial blockage than for a conventional valve having an annular passageway of the same throughput.